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halo2_gadgets: Deduplicate some Sinsemilla chip expressions

This commit is contained in:
Jack Grigg 2022-05-07 23:17:59 +00:00
parent 6444ccc16f
commit dc2ec0308d
2 changed files with 38 additions and 30 deletions
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53
halo2_gadgets/src/sinsemilla/chip.rs
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@ -88,6 +88,38 @@ where
pub fn lookup_config(&self) -> LookupRangeCheckConfig<pallas::Base, { sinsemilla::K }> {
self.lookup_config
}
/// Derives the expression `x_r = lambda_1^2 - x_a - x_p`.
fn x_r(
&self,
meta: &mut VirtualCells<pallas::Base>,
rotation: Rotation,
) -> Expression<pallas::Base> {
let x_a = meta.query_advice(self.x_a, rotation);
let x_p = meta.query_advice(self.x_p, rotation);
let lambda_1 = meta.query_advice(self.lambda_1, rotation);
lambda_1.square() - x_a - x_p
}
/// Derives the expression `Y_A = (lambda_1 + lambda_2) * (x_a - x_r)`.
#[allow(non_snake_case)]
fn Y_A(
&self,
meta: &mut VirtualCells<pallas::Base>,
rotation: Rotation,
) -> Expression<pallas::Base> {
let x_a = meta.query_advice(self.x_a, rotation);
let lambda_1 = meta.query_advice(self.lambda_1, rotation);
let lambda_2 = meta.query_advice(self.lambda_2, rotation);
(lambda_1 + lambda_2) * (x_a - self.x_r(meta, rotation))
}
/// Derives the expression `q_s3 = (q_s2) * (q_s2 - 1)`.
fn q_s3(&self, meta: &mut VirtualCells<pallas::Base>) -> Expression<pallas::Base> {
let one = Expression::Constant(pallas::Base::one());
let q_s2 = meta.query_fixed(self.q_sinsemilla2, Rotation::cur());
q_s2.clone() * (q_s2 - one)
}
}
/// A chip that implements 10-bit Sinsemilla using a lookup table and 5 advice columns.
@ -184,20 +216,10 @@ where
// Closures for expressions that are derived multiple times
// x_r = lambda_1^2 - x_a - x_p
let x_r = |meta: &mut VirtualCells<pallas::Base>, rotation| {
let x_a = meta.query_advice(config.x_a, rotation);
let x_p = meta.query_advice(config.x_p, rotation);
let lambda_1 = meta.query_advice(config.lambda_1, rotation);
lambda_1.square() - x_a - x_p
};
let x_r = |meta: &mut VirtualCells<pallas::Base>, rotation| config.x_r(meta, rotation);
// Y_A = (lambda_1 + lambda_2) * (x_a - x_r)
let Y_A = |meta: &mut VirtualCells<pallas::Base>, rotation| {
let x_a = meta.query_advice(config.x_a, rotation);
let lambda_1 = meta.query_advice(config.lambda_1, rotation);
let lambda_2 = meta.query_advice(config.lambda_2, rotation);
(lambda_1 + lambda_2) * (x_a - x_r(meta, rotation))
};
let Y_A = |meta: &mut VirtualCells<pallas::Base>, rotation| config.Y_A(meta, rotation);
// Check that the initial x_A, x_P, lambda_1, lambda_2 are consistent with y_Q.
meta.create_gate("Initial y_Q", |meta| {
@ -215,12 +237,7 @@ where
meta.create_gate("Sinsemilla gate", |meta| {
let q_s1 = meta.query_selector(config.q_sinsemilla1);
// q_s3 = (q_s2) * (q_s2 - 1)
let q_s3 = {
let one = Expression::Constant(pallas::Base::one());
let q_s2 = meta.query_fixed(config.q_sinsemilla2, Rotation::cur());
q_s2.clone() * (q_s2 - one)
};
let q_s3 = config.q_s3(meta);
let lambda_1_next = meta.query_advice(config.lambda_1, Rotation::next());
let lambda_2_cur = meta.query_advice(config.lambda_2, Rotation::cur());

15
halo2_gadgets/src/sinsemilla/chip/generator_table.rs
View File

@ -39,10 +39,7 @@ impl GeneratorTableConfig {
meta.lookup(|meta| {
let q_s1 = meta.query_selector(config.q_sinsemilla1);
let q_s2 = meta.query_fixed(config.q_sinsemilla2, Rotation::cur());
let q_s3 = {
let one = Expression::Constant(pallas::Base::one());
q_s2.clone() * (q_s2.clone() - one)
};
let q_s3 = config.q_s3(meta);
// m_{i+1} = z_{i} - 2^K * (q_s2 - q_s3) * z_{i + 1}
// Note that the message words m_i's are 1-indexed while the
@ -55,17 +52,11 @@ impl GeneratorTableConfig {
let x_p = meta.query_advice(config.x_p, Rotation::cur());
// y_{p,i} = (Y_{A,i} / 2) - lambda1 * (x_{A,i} - x_{P,i}),
// where Y_{A,i} = (lambda1_i + lambda2_i) * (x_{A,i} - x_{R,i}),
// x_{R,i} = lambda1^2 - x_{A,i} - x_{P,i}
//
// y_{p,i} = (Y_{A,i} / 2) - lambda1 * (x_{A,i} - x_{P,i})
let y_p = {
let lambda1 = meta.query_advice(config.lambda_1, Rotation::cur());
let lambda2 = meta.query_advice(config.lambda_2, Rotation::cur());
let x_a = meta.query_advice(config.x_a, Rotation::cur());
let x_r = lambda1.clone().square() - x_a.clone() - x_p.clone();
let Y_A = (lambda1.clone() + lambda2) * (x_a.clone() - x_r);
let Y_A = config.Y_A(meta, Rotation::cur());
(Y_A * pallas::Base::TWO_INV) - (lambda1 * (x_a - x_p.clone()))
};